Transforming growth factor beta induces mesangial cell apoptosis through NO- and p53-dependent and -independent pathways

Background: Because transforming growth factor beta (TGF-beta) has been sho wn to have a bimodal effect on mesangial cell (MC) proliferation, we studie d its effect on MC apoptosis, Methods: Cultured mouse MCs were used to evaluate the effect of TGF-beta, M orphologic evaluation of MC apoptosis was performed by staining cells with H-33342 and propidium iodide, To confirm the effect of TGF-beta on MC apopt osis, DNA was extracted from control and TGF-beta -treated MCs and run on g el electrophoresis, We evaluated the effect of N-G-nitro-L-arginine methyl ester (L-NAME), a nitric oxide (NO) synthase inhibitor, on TGF-beta -induce d MC apoptosis to determine the role of NO and studied the effect of sodium nitroprusside (SNP) and SNAP (S-nihoso-N-acetyl-penicillamine) on MC apopt osis to confirm the effect of NO, We examined the role of p53 by studying t he effect of TGF-beta on MCs derived from p53 knockout mice (p53KO-MC) as w ell as a normogenic strain (N-MC). We also examined the effect of TGF-beta, SNP, and SNAP on apoptosis of p53 mutant (MDAMB-231) and wild-type p53 (MC F-7) breast cancer cell Lines, In addition, Western blots were generated fr om control, TGF-beta -treated, and SNAP-treated MCs and probed for the expr ession of p53, Results: TGF-beta promoted MC apoptosis, Moreover, TGF-beta -treated MCs di splayed integer multiples of 180 base pairs (ladder pattern), L-NAME inhibi ted TGF-beta -induced MC apoptosis, Furthermore, SNP and SNAP, NO donors, p romoted MC apoptosis, TGF-beta also enhanced the MC expression of p53, TGF- beta induced only a moderate degree of apoptosis in MCs derived from p53KO- MC when compared with N-MCs, Similarly, the TGF-beta -induced apoptosis of MDAMB-231 was of a moderate degree when compared with MCF-7 cells, Conclusions: We hypothesize that TGF-beta promotes MC apoptosis through NO generation and p53-dependent and -independent pathways.